Hello,
can someone help me, how to create a 2 column list for my categories? I got lots of categories and I think it looks better if the list is shown in 2 columns.

Cheers,
Denis
Add some custom CSS to the admin for that post type and set the LI elements to float left and 50% width.
add_action{'admin_head', 'my_customs_admin_css');
function my_customs_admin_css() {
?>
<style type="text/css">
/* "test field name" is the name of the field I used for this */
div[data-name="test field name"] ul.acf-checkbox-list li {
float: left;
width: 50%;
}
</style>
<?php
}